Add server/cache support to gaeconfig.

common/config/impl/erroring/erroring.go

-// Copyright 2015 The LUCI Authors. All rights reserved.
-// Use of this source code is governed under the Apache License, Version 2.0
-// that can be found in the LICENSE file.
-
-// Package erroring implements config.Interface that simply returns an error.
-//
-// May be handy as a placeholder in case some more useful implementation is not
-// available.
-package erroring
-
-import (
-        "net/url"
-
-        "golang.org/x/net/context"
-
-        "github.com/luci/luci-go/common/config"
-)
-
-// New produces config.Interface instance that returns the given error for all
-// calls.
-//
-// Panics if given err is nil.
-func New(err error) config.Interface {
-        if err == nil {
-                panic("the error must not be nil")
-        }
-        return erroringImpl{err}
-}
-
-type erroringImpl struct {
-        err error
-}
-
-func (e erroringImpl) ServiceURL(ctx context.Context) url.URL {
-        return url.URL{
-                Scheme: "error",
-        }
-}
-
-func (e erroringImpl) GetConfig(ctx context.Context, configSet, path string, hashOnly bool) (*config.Config, error) {
-        return nil, e.err
-}
-
-func (e erroringImpl) GetConfigByHash(ctx context.Context, contentHash string) (string, error) {
-        return "", e.err
-}
-
-func (e erroringImpl) GetConfigSetLocation(ctx context.Context, configSet string) (*url.URL, error) {
-        return nil, e.err
-}
-
-func (e erroringImpl) GetProjectConfigs(ctx context.Context, path string, hashesOnly bool) ([]config.Config, error) {
-        return nil, e.err
-}
-
-func (e erroringImpl) GetProjects(ctx context.Context) ([]config.Project, error) {
-        return nil, e.err
-}
-
-func (e erroringImpl) GetRefConfigs(ctx context.Context, path string, hashesOnly bool) ([]config.Config, error) {
-        return nil, e.err
-}
-
-func (e erroringImpl) GetRefs(ctx context.Context, projectID string) ([]string, error) {
-        return nil, e.err
-}